Patient beds in healthcare facilities are designed so that various parts of the bed can adopt a number of positions to provide for greater patient comfort and/or to facilitate the tasks of an attendant, for example a nurse. For example, beds may be raised or lowered to different heights. Patient support platforms may be tilted to achieve the Trendelenburg and reverse Trendelenburg positions. Patient support platforms may comprise back rests and/or knee rests that can be raised or lowered to support a patient's back and knees in a variety of positions.
Adjusting the position of the bed or parts of the bed may be accomplished by a variety of means, for example, by mechanical, hydraulic and electrical means and combinations thereof. Purely mechanical means, including linkages, gears, cranks, etc., have traditionally been used but generally require manual power for their operation. Consequently, physical limitations of the bed's operator represent significant limitations to the design of beds where position changes are accomplished solely by mechanical means. The additional use of hydraulics permits bed design where the physical limitations of the operator are less of a factor. However, the use of electrical components, for example motors, switches, electronic controllers, etc., in combination with mechanical and/or hydraulic components has greatly simplified the design and use of patient beds throughout the healthcare industry. Beds designed with electrical components permit extensive operation of the bed with minimal operator effort.
Electrically operated patient beds are generally equipped with a plurality of switches to control the various adjustments that can be made to the bed. Switches are often localized on a single control panel for easy access by an operator. Where access to the switches by the patient is undesirable, the control panel may be located in an area of the bed that is normally inaccessible to the patient in the bed, for example, on the outside face of the foot board.
Despite the flexibility offered by the use of electrical components, there remains limitations, often driven by regulatory considerations, to the use of electrical components in patient beds. Thus, in a number of instances, mechanical means are still used for some operations of the bed. This is particularly evident in the design of emergency systems for patient beds.
Design of medical electrical equipment is regulated by International Standards. In particular, two standards applicable to electrically operated patient beds are:                UL 2601-1, the Underwriters Laboratories Inc. Standard for Safety, Medical Electrical Equipment, Part 1: General Requirements for Safety (1997); and,        IEC 601-2-38 International Standard, Medical Electrical Equipment—Part 2: Particular requirements for the safety of electrically operated hospital beds (1996).        
According to Section 22.4 of UL 2601-1,                “Movements of EQUIPMENT or EQUIPMENT parts which may cause physical injury to the PATIENT shall be possible only by the continuous activation of the control by the OPERATOR of these EQUIPMENT parts.”        
According to Section 22.4.101 of IEC 601-2-38,                “Electrically powered functional movements of the BED shall be possible only by means of MOMENTARY CONTACT SWITCHES.”        
Momentary Contact Switch is defined in Section 2.1.106 of IEC 601-2-38:                “Control device which initiates and maintains operation of operating elements only as long as the control (actuator) is actuated. The manual control (actuator) returns automatically to the stop position when released. MOMENTARY CONTACT SWITCHES are also known as “hold-to-run control devices”.”        
In an emergency situation, for instance when a patient has a heart attack or goes into shock, an attendant must quickly perform emergency procedures on the patient, for example CPR (cardiopulmonary resuscitation). However, a patient in a patient bed, may be in any number of positions at the onset of the emergency. For instance, the back and knee rests may be raised so that the patient is in a sitting position, for example, to watch television, to eat, etc. In such an instance, it is necessary for the back and knee rests to be lowered quickly to a flat position so that emergency procedures may be administered more effectively. It is desirable, therefore, that the bed have a system by which the back and knee rests may be lowered quickly to the flat position, while at the same time permitting the attendant to begin administering emergency procedures.
However, in light of the above-noted standards, all electrical control of moving parts on an electrically operated patient bed has heretofore been by way of momentary contact switches. Since momentary contact switches turn off the functioning of a moving part when the switch is released, electrical activation of an emergency system on a patient bed has been heretofore considered impossible within the context of the above-noted standards. Instead, emergency systems on patient beds have been designed to activate manually, even on beds otherwise electrically operated, in order to remain within the above-noted standards.
Therefore, there is a need in the art for an electrically activated emergency system on a patient bed, which meets the regulatory requirements of the standards governing electrically operated patient beds.